Conventionally, in the case of exposing a pattern of a mask to a work by means of a UV-irradiation apparatus, it is required to align the mask and the work to the appropriate exposure position. For this reason, various alignment processes have been suggested.
As shown in FIG. 14(a) and FIG. 14(b), in the case of aligning the work and the mask, the previous alignment which aligns the position of the work W placed on a work mounting plate 52 is carried out by using a previous alignment means (not shown) which is previously aligns the positions of the mask and the work W. Subsequently, the mask M placed on the upper side of the work mounting plate 52 or on any other portion is moved so that the work W and the mask M are placed in a face-to-face manner, and the work W and the mask M are come into contact with each other and adhered to each other by means of a vacuum suction mechanism (not shown).
When the work W the mask M are come into contact with each other and adhered to each other, the cameras such as CCD cameras are moved to the position to be picked up, pick up and recognize the work mark Wm (typically at least two marks) and mask mark Mm (typically at least two marks), and the amount of shear in the center positions of both marks Wm and Mm is calculated by a recognizing and calculating control means 53.
Furthermore, when being aligned, in the case where the work mounting plate 52 is an alignment mounting table which is movable, the situation of adhering the work W and the mask M is released, the alignment mounting table is controlled and moved by the control signal from the recognizing and calculating control means 53 on the basis of the calculated amount of shear in the positions to complete a series of the alignment operations.
In the case where the mask M is aligned by means of a three point locator shown by an ideal line (configured by pushing a frame for supporting the mask or edge surfaces of the three sides of the mask M by a pushing means), the adhering of the work W and the mask M is released, the mask M is controlled and moved by means 54 for moving the three point locator utilizing the control signal from the recognizing and calculating control means 53 on the basis of the calculated amount of shear in the positions to complete a series of the alignment operations. (see FIG. 14(c).
In order to carry out these alignment operation in an adequate manner, as shown in FIG. 14(b), it is required to recognize both marks Wm and Mm within the picked out display by the camera. In addition, in the case where the work mark Wm and the mask mark Mm can be picked up, these marks Wm and Mm are recognized by contrast (converted into binary data), the center positions of these marks Wm and Mm are calculated, and the amount of the shear in the positions of both marks Wm and Mm is calculated to find the amount of the work M or the mask M to be moved.
When the mask mark Mm and the work mark Mm are picked up by the camera 50, as shown in FIG. 14(a) by the real line, an illumination lamp 51 for picking up the image is placed on the side of the camera 50, and additionally utilizing the reflect light from the illumination lamp, the more vivid images are picked up. As shown in FIG. 14(a) by the ideal line, the illumination lamp 51 is placed opposite the camera 50, and a transmitting light is additionally utilized to pick up more vivid images. For this reason, the utilization of the reflect light or the transmitting light is changed according to the configuration of the apparatus.
However, the configuration of the conventional alignment mechanisms for aligning the work W and the mask M have the following problems.
When the alignment of the work W and the mask M is carried out, the operation of the aligning the work W and the mask M is carried out after the previous alignment of the work W has been finished. When the previous alignment of the work W is carried out, each of the edge surfaces of the work is pushed to carry out the previous alignment in the direction of the center of the work W.
For this reason, depending upon the configuration of the edges of the work, there is a situation that the work W is previously aligned at the position out of the predetermined position. In such a case, as shown in FIG. 14(d) when both marks Wm and Mm are picked up by a camera, the small black circular mask mark Mm is positioned except for inside of the large white circular work mark Wm. In this case, since color of the work W near the mask mark Mm is black as a rule, the black circular mask mark Mm is embedded on the color of the work W. For this reason, when being picked up by the camera, the mask mark Mm cannot be recognized, even if reflecting light or penetrating light is used as lighting.
Alternatively, depending upon the shape of the edge surface of the work W, there is a situation that the work W is previously aligned at the position out of the predetermined position. In such a case, as shown in FIG. 14(d), the mask mark Mm is sometimes positioned on the boarder line of the work mark Wm, when both marks Wm and Mm are picked up by the camera. In such a case, a recognition processing control means 53 cannot recognize the work mark Wm and the mask mark Mm in their normal shapes.
Consequently, if the mask mark Mm cannot be recognized by said image processing means 50, the previous alignment of the work W must be undone. This makes the series of operations such as vacuum depositing between the work W and the mask M, camera operation to carry out again, it is much time to carry out alignment, and there sometimes arises a situation where no appropriate operation can be carried out. In particular, in the case of an exposing apparatus, which is automatically run, the operations such as carrying in, transferring, aligning, exposing, and carrying out should be disadvantageously stopped.
In the conventional alignment means, since there is a configuration that the edge portion of the work W is pushed to conduct the previous alignment in the direction of the center of the work W.